US President Barack Obama has ordered intelligence agencies to review cyber attacks and foreign intervention in last month's US election, as reports emerged the CIA has concluded Russia intervened to help President-elect Donald Trump win the White House.

Key points:

US senators reportedly told it was "quite clear" that electing Mr Trump was Russia's goal

Mr Obama's official said White House wants "full review" of 2016 election process

Mr Trump's teams doesn't address reports in statement on the issue

Mr Obama's homeland security adviser Lisa Monaco said the report into the review would be delivered before he left office on January 20 and the findings would be shared with politicians and other stakeholders.

"The President has directed the intelligence community to conduct a full review of what happened during the 2016 election process," Ms Monaco said.

"And to capture lessons learned from that and to report to a range of stakeholders, to include the Congress."

The report said the CIA found the intention was not only to undermine confidence in the US electoral system, but briefers have told US senators it was "quite clear" that electing Mr Trump was Russia's goal.

The officials in the Post described the individuals as people known to the intelligence community who were part of a wider Russian operation to boost Mr Trump and reduce Mrs Clinton's chances of winning the election.

"It is the assessment of the intelligence community that Russia's goal here was to favour one candidate over the other, to help Trump get elected," the Post quoted a senior US official as saying.

Mr Obama has said he warned Russian President Vladimir Putin about consequences for the attacks, but Russian officials have denied all accusations of interference.

A CIA spokeswoman said the agency had no comment on the report.

Mr Trump has said he is not convinced Russia was behind the cyber attacks and his transition team issued a statement on "claims of foreign interference in US elections" on Friday, but did not directly address the issue.

'New threshold' in election-related 'malicious cyber activity'

Ms Monaco said cyber attacks were not new but might have crossed a "new threshold" this year.

When she was working as a senior FBI official in 2008, she said, the agency alerted the presidential campaigns of then-senator Mr Obama and Republican Senator John McCain that China had infiltrated their respective systems.

"We've seen in 2008 and in this last election system malicious cyber activity," Ms Monaco said.

Asked if Mr Trump's transition team was not concerned enough about Russia's influence on the election or about other threats to the United States such as infectious disease outbreaks, Ms Monaco said it was too soon to say.